Signaling system



a 1,629,093 May 1927' A. M. CURTIS o S IGNALING SYSTEM I Filed Dec. 1923 IIIIIIIIIIA 1.4 IIIIIIIIIIIIIIIIIIIII'I. X5

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YORK.

UNITED STATES PATENTVOFVFICE.

AUSTEN M. CURTIS, OF EAST ORANGE, NEW JERSEY, ASSIGNOB TO WESTERN ELEC- TRIC COMPANY, INCORPORATED, NEW YORK, N. Y., A CORPORATION OF NEW SIGNALING SYSTEM.

Application filed December 8, 1823. Serial No. 679,315.

This invention relates, in general, to the prevention of interference in signaling systems caused by sparking at the contacts of relays, distributors, tuning forks and similar apparatus which operate in the vicinity of amplifying apparatus, and more partipularly the prevention of such interference in submarine cable systems.

In submarine cable telegraph operation, in which printing telegraph apparatus is employed, a great deal of difiiculty has been experienced due to interference resulting from the operation of nearby apparatus in which electrical circuits are opened and made, causing sparking at the contacts. This disturbance may be the result of sparking occurring in various pieces of apparatus mounted at difi'erent locations so that it is ver dnfficult, if not impossible, to eliminate t e CllS- turbance by orienting the amplifying apparatus. In certain cases, complete shielding of a submarine cable receiving amplifier, in addition to orienting it with respect to a source of very weak interfering waves, has been found ineffective in preventing interference. The present invention is the'result of an investigation to determine the cause of interference under these conditions.

It was found that contactsparks, even when imperceptible by ordinary means, generate trains of free electric waves of sufiicient intensity to cause signal distortion, and cover a wide band of frequencies including some so high that a six inch loop of wire is a very high impedance for them. If these waves are allowed to reach the grid of a vacuum tube in any stage of a vacuum tube amplifier they are partly or wholly rectified, and transmitted through the amplifier as low frequency impulses, which are frequently many times stronger than'the incoming signals. As the amplifiers in the submarine telegraphy s stems under investigation transmitted a. and of frequencies varying from about cycle to about 200 cycles, it might be thought that a low pass filter, of the usual type inserted in the line and cutting out frequencies above 200 cycles, would be all that was necessary, but it was found that such a filter is entirely useless.

It is the object of the present invention to protect an amplifier from such disturbances of high frequency. To accomplish this object, there is provided a low .pass

filter so mounted with respect to the amplifier that danger of objectionable pick-up is practically eliminated. Brie-fly stated, the reactive elements of the filter are mounted so close to the amplifier elements that the necessary electrical connections can be made prising a low pass filter and a vacuum tube amplifier and Fig. 2 is a view, partly in sec tion, of a vacuum tube amplifier in the socket of which is mounted a condenser, which ordinarily forms one element of the low pass filter.

Referring to the drawing, a non-inductive resistance 5 which may be short-circuited by the closure of switch 6, and an inductance 7 which may be short-circuited by means of switch '8, are connected in series with the grid of the amplifier 9. These elements, together with the condenser connected between the filament and grid of the amplifier, constitute a low pass filter. Both the inductance and the'condenser are mounted as close to the vacuum tube amplifier as is possible, and the switch 8 is-arranged so that the lead connected to the amplifier side of the inductance is of minimum length. Preferably, the condenser 10 is mounted within the socket 11 of the amplifier in order to eliminate all Wiring in so far as it is possible since in some cases it has been found that the interposition of a few inches of wire between the condenser and the grid and filament of the amplifier is almost equivalent to entirely disconnecting the condenser. The condenser, therefore, may be mounted, as shown, in Fig. 2, in which case it is supported by springs 12, 12, which are held rigidly by the terminal screws .13, 13. The springs 12, 12 have right angle portions 14, 14 struck up so as to engage with springs 15, 15 When the amplifier tube is inserted in the socket.

In certain casesit may be found desirable to employ only the inductance coil, and the condenser mounted as described above, in which case the switch 6 may be closed. Under other conditions such an arrangement may produce oscillations, in which case the switch 6 is opened and the resistance serves to dam n the oscillations. Under, still other co nd1tions it may be advisable to close switch 8, leaving switch 6 open and thereby eliminat-ing difiiculty due to pick-up byv the in ductance coil 7 g which may be the equivalent of a loop antenna. If the inductance coil alone is used with "a condenser it may be possible to largely eliminate any disturbance caused by electromagnetic induction by orienting the coil, if but one source of sparking -is present. In practice, however, there are case when operating at high speed, since...

without such a device it is possible to employ printing telegraph apparatus in submarine cable only by reducing the speed of transmission to a point where pick-up is much weaker than the received signals.

The invention claimed is:

1. In a low frequency signaling system subject to high frequency extraneous disturbances, an amplifier, a series reactance in the input circuit of said amplifier and mounted immediately adjacent thereto, and a condenser mounted immediately adjacent said amplifier and connected directly between the input terminals thereof without leads of appreciable length. I

2. In a low frequency signaling system subject tohigh frequency extraneous disturbances, an amplifier comprising a filament and a grid, terminals therefor, and a condenser having its terminals substantially in alignment with said grid and filaand a grid, a mounting socket equipped with terminal springs for said amplifier, and a condenser mounted within the socket and having its terminals connected between the grid and filament sprin of said socket.

4. In a submarine cab e signal amplifying system subject to high frequency extraneous disturbances an amplifier, a series reactance in the input circuit of said amplifier and mounted immediately adjacent thereto and a condenser mounted immediately adjacent said amplifier and connected directly between the input terminals thereof without leads of appreciable length, said reactance and condenser together constituting a filter for preventing disturbances outside the submarine signaling frequency range from reaching said amplifier.

5. In a low frequency signaling system subject to high frequency extraneous disturbances, a space discharge repeating device including a cathode, an anode and an impedance control element, spaced terminals for said cathode and impedance control elements rigidly connected to said device, an impedance and a condenser in the input circuit of said I device and forming a low pass filter, said impedance being mounted immediately adjacent said device, and

means for associating said condenser with said spaced terminals without appreciable leads.

In witness whereof, I hereunto subscribe my name this first day of December A. D., 1923.

AUSTEN M. CURTIS.- 

